1. Field of the Invention
The present invention relates to an optical modulator and an image projection display apparatus using it and particularly, to an image projection display apparatus using it, capable of reducing a size of a system and improving efficiency, by manufacturing a reflective optical modulator.
2. Description of the Background Art
Conventionally, an one-dimensional optical modulator modulates an incident light by diffracting the light and as a typical one-dimensional optical modulator, there is a Grating Light Valve (GLV) of the Silicon Light Machine (SLM) Co in the US.
The GLV is reflective and has excellent speed and contrast characteristics. Accordingly the GLV is spotlighted as a modulator for displaying for the next generation, but it can not be applied to products of common use.
The structure of the GVL and operational characteristics will be described in detail with reference to FIGS. 1, 2A and 2B.
FIG. 1 is a perspective view showing a GLV in accordance with the conventional art, FIG. 2A is a pattern diagram illustrating a case that a voltage is not applied to the GLV in accordance with the conventional art, and FIG. 2B is a pattern diagram illustrating a case that a voltage is applied to the GLV in accordance with the conventional art.
As shown in FIG. 1, the GLV includes a substrate 1 which is composed of a silicon chip, and a plurality of ribbons 2 which are installed on the substrate 1, for reflecting a light.
The both sides of the respective ribbons 2 are fixed to the substrate 1, and the center portion (upper surface) is designed to be a predetermined distance apart from the substrate 1. Also, the plurality of ribbons 2 are connected with a means to which a voltage is alternately applied.
The ribbons of the GVL are under a same condition in case a voltage is not applied and when a voltage is applied to the GLV, the means to which the voltage is applied and the connected ribbons 2 are bent to the substrate 1 side, form a grating corresponding to the incident light from the outside, and modulate the light by using diffraction by the grating.
That is, as shown in FIG. 2A, if a voltage is not applied to the ribbons 2, the ribbons 2 are positioned on a same plane. At this time, when a light is made incident vertically in parallel, the ribbons 2 function as a mirror surface, thus to directly reflect the light.
As shown in FIG. 2B, when a voltage is alternatively applied to the plurality of ribbons 2, the ribbons 2 to which the voltage is applied is bent to the substrate 1 side and the upper surface of the ribbons 2 is formed in a latticed structure, thus to diffract a light which is irradiated vertically. As the incident light is diffracted by the ribbon-latticed structure, the incident light is modulated.
The GLV which is an one-dimensional optical modulator controls a distance along the incident wave length that the ribbon 2 descends. At this time, to obtain an optimal efficiency, the distance that the ribbon 2 descends must be xc2xc of the wave length (xcex) of the incident light.
However, the operation of the GLV is a mechanical operation according to application of a voltage and there occurred a problem that the bent distance of the ribbon could not be accurately controlled as xc2xc of the wave length of the incident light. Also, in case the ribbon 2 which is bent to the substrate 1 side reaches to the substrate 1 in driving the GLV, the ribbon was not recovered to the original state even if the application of the voltage is stopped and the substrate was stuck on the substrate. Therefore, the GLV could not be used.
Therefore, an object of the present invention is to provide an optical modulator and an image projection display apparatus, capable of reducing a size of a system and improving efficiency, by excluding mechanical factors and using an optical modulator in which a reflection plane is attached to a nonlinear matter.
To achieve these and other advantages and in accordance with the purpose of the present invention, as embodied and broadly described herein, there is provided an optical modulator, including a nonlinear matter which is divided into predetermined regions having a direction of a polarization which is periodically reversed, an electrode which is joined with the upper and lower sides of the nonlinear matter, for applying an electric field to the polarization region at the lower portion of the nonlinear matter and a reflection plane which is joined to the rear surface of the nonlinear matter, for reflecting an incident light to an incident region again.
To achieve these and other advantages and in accordance with the purpose of the present invention, as embodied and broadly described herein, there is provided a method for fabricating an optic modulator, including the steps of positioning a plurality of electrodes in the upper and lower portions of a nonlinear matter, forming a plurality of regions having polarization which is periodically reversed by reversing the polarization by applying a power source to the electrode, composing a plurality of pixels by grouping a plurality of polarization regions in pairs after removing all of the electrodes, controlling the state of the light which is projected in each pixel by forming a plurality of electrodes which are mutually separated, in the respective pixels and coating a material which can reflect a light to the respective plural pixels on an opposite side of the incident region.
To achieve these and other advantages and in accordance with the purpose of the present invention, as embodied and broadly described herein, there is provided an image projection display apparatus using a reflective optical modulator, including a light source 150 for irradiating a light, a breaker plane 140 which is positioned in the upper portion of the light source 150, for reflecting the light of the light source into an one-dimensional optical modulator and intercepting a light which is not diffracted in the one-dimensional optical modulator 160, a collimating lens 130 for focusing the light which is diffracted in the one-dimensional optical modulator 160, a focusing lens 120 for focusing the light of the collimating lens and a Galvano meter 100 for irradiating an image plane by reflecting the light which is irradiated through the focusing lens 120.
The foregoing and other objects, features, aspects and advantages of the present invention will become more apparent from the following detailed description of the present invention when taken in conjunction with the accompanying drawings.